• Nuclear Engineering and Technology
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• 제55권1호
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• pp.12-24
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• 2023

With the improvement of laser technology, the strategic needs of efficient and precise decontamination of various components in nuclear application units can be fulfilled by laser decontamination. The surface contaminants of nuclear facilities mainly exist both as loose contaminated layer and fixed oxide layer. The types of radionuclides and contamination layer thickness are closely related to the operation status of nuclear facilities, which have an important influence on the laser decontamination process. This study reviewed the mechanism of laser surface treatment and the influence of laser process parameters on the decontamination thickness, decontamination factor, decontamination efficiency and the distribution of aerosol particle. Although multiple studies have been performed on the mechanism of laser processing and laser decontamination process, there are few studies on the microscopic process mechanism of laser decontamination and the influence of laser decontamination on surface properties. In particular, the interaction between laser and radioactive contaminants needs more research in the future.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2018년도 춘계학술논문요약집
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• pp.235-236
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• 2018

• Journal of Radiation Protection and Research
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• 제23권1호
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• pp.7-15
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• 1998

몇 종류의 제염제에 대한 제염효과를 평가하기 위해 $^{60}Co$과 $^{137}Cs$에 의한 피부오염의 제염실험을 수행하였다. 본 연구에서는 인체피부 대신에 돼지피부를 활용하였으며, 피부오염용액으로는 $^{60}CoCl_2$와 $^{137}CsCl$ 용액을 사용하였다. 그리고 제염제로는 현재 사용되고 있는 비눗물, EDTA 외에 오염된 구조물의 표면오염 제거를 위해 원자력연구소에서 개발한 KAERICON과 본 연구를 통해 제조한 IOCON, TRICON 및 CHARCON 등을 이용하여 피부오염에 대한 제염을 실시하여 각 제염제의 제염효과를 평가하였다. 방사성물질의 피부침투정도를 파악하기 위하여 16시간동안 방사성물질을 시료표면에 점착시킨 후 감마선 측정을 통해 침투율을 평가하였으며, 이 실험에서 $^{137}Cs$의 경우 11.5%, $^{60}Co$의 경우 3.2% 정도가 피부로 침투됨을 알 수 있었다. 각 제염제의 제염효과를 평가해본 결과 KAERICON은 $^{137}Cs$에 대하여 최고 52.1%(제염계수 2.1)의 제염율을 나타내었으며, IOCON도 $^{137}Cs$에 대하여 비교적 좋은 제염율(제염계수 1.9)을 나타내었다. 그러나 $^{60}Co$에 대해서는 IOCON, CHARCON 모두 20%(제염계수 1.2) 미만의 제염율을 나타내었으며, KAERICON도 $^{60}Co$에 대해 낮은 제염율(제염계수 1.1)을 나타내었다. TRICON은 $^{137}Cs$에 대해 $1.6{\sim}1.8$의 제염계수를 나타내었으며, $^{60}Co$에 대해서는 $1.0{\sim}1.2$의 제염계수를 나타내었다.

• Journal of Radiation Protection and Research
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• 제25권2호
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• pp.99-107
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• 2000

플라즈마 아크 용융방식 유리화 시험설비의 계통내 기체 및 최종배출구 전단의 배기체를 분석함으로써 배기체중에 포함된 분석용 첨가물의 거동 및 배기가스 처리장치의 제염성능을 평가하였다. 중금속 물질(Pb, Cd, Hg), 방사성 모의물질(Co, Cs) 그리고 방사성핵종($^{60}Co,\;^{137}Cs$)을 분석용 첨가물로 사용한 실험결과로부터 첨가물질의 거동에 따른 유리화 설비 배기체처리시스템의 제염특성 및 제염제수를 구하였다.

• 시스템엔지니어링학술지
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• 제17권1호
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• pp.11-20
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• 2021

Decontamination of systems, structures and components (SSC) during the decommissioning of a Nuclear Power Plant (NPP) can be for a variety of reasons. The main reasons for decontamination are: to reduce the contamination of SSC to a reasonably low level, to reduce the potential for the spread of contaminants into the environment and to reduce the cost of disposal due to the reduced level of contamination in a particular SSC. The decontamination technique can be aggressive or non-aggressive depending on the intent after the decontamination process. Aggressive decontamination technique is used when the intent is not to reuse the SSC while a non-aggressive decontamination technique is used with the intent of SSC reuse. For different SSCs there are different decontamination techniques that can be used, each having its own advantages and drawbacks. Metal components such as pipes in the nuclear power plant account for a large amount of nuclear wastes generated. Some of these wastes can be reused if the contaminant level is reduced to an acceptable level. Laser ablation is a non-aggressive decontamination technique that can be used to reduce the contamination in pipes to an acceptable level with no secondary waste generated during the process. The operation and control of a laser ablation device must be precise to achieve a high decontamination factor. This precision can be achieved by a well-designed motion control system. For this purpose, a motion control system was developed consisting of two parts: the first part being the precise control of the laser ablation device inside the pipe and the second part is the control of the laser ablation device outside the pipe. This paper describes the Systems Engineering approach for the development process of a motion control system for the Laser decontamination system.

• 방사성폐기물학회지
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• 제12권1호
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• pp.79-88
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• 2014

원자력이용시설에서 발생한 작은 크기의 금속 조각들을 효과적으로 제염하는 스마트 장치를 개발하였다. 이 장치는 자성연마재를 포함한 영역의 자속밀도를 연속적으로 변화시키는 방법과 초음파를 이용하는 다중 제염장치이다. 한편, 제염 효율을 높이기 위해 제염 장치가 제염 대상 전체에 작용하도록 장치들의 구성을 수정하였다. 개발된 장치들의 최적 작동조건을 도출하여 샘플로 선정한 소형의 금속방사성페기물에 대하여 자기장과 초음파제염을 각각 15분간 실시하였다. 그 결과 제염계수의 범위는18~56으로 크게 향상되었으며 제염 후 모든 샘플은 백그라운드(BKG)값 이하로 확인되었다.

• 방사성폐기물학회지
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• 제19권1호
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• pp.51-58
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• 2021

Chemical decontamination of primary systems in a nuclear power plant (NPP) prior to commencing the main decommissioning activities is required to reduce radiation exposure during its process. The entire process is repeated until the desired decontamination factor is obtained. To achieve improved decontamination factors over a shorter time with fewer cycles, the appropriate flow characteristics are required. In addition, to prepare an operating procedure that is adaptable to various conditions and situations, the transient analysis results would be required for operator action and system impact assessment. In this study, the flow characteristics in the steady-state and transient conditions for the chemical decontamination operations of the Kori-1 NPP were analyzed and compared via the MARS-KS code simulation. Loss of residual heat removal (RHR) and steam generator tube rupture (SGTR) simulations were conducted for the postulated abnormal events. Loss of RHR results showed the reactor coolant system (RCS) temperature increase, which can damage the reactor coolant pump (RCP)s by its cavitation. The SGTR results indicated a void formation in the RCS interior by the decrease in pressurizer (PZR) pressure, which can cause surface exposure and tripping of the RCPs unless proper actions are taken before the required pressure limit is achieved.

• 방사성폐기물학회지
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• 제2권3호
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• pp.219-230
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• 2004

Most of the low-level liquid radioactive wastes generated from PWR plants are classified into high or low total suspended solid(HTDS or LTDS), and into radiochemical and radioactive laundry waste. Although the evaporation process has a high decontami- nation ability, it has several problems such as corrosion, foam, and congestion. A new liquid waste disposal process using the ion-exchange demineralizer(IED), instead of the current evaporation process, has been introduced into the Yonggwang NPP #5 and 6. These two methods have been compared to understand the differences in this study. Aspects compared here were the released radioactivity amount of the liquid radioactive wastes, the dose of off-site residents, the decontamination factor, and the amount of the solid radioactive wastes. The IED system is designed to discharge higher radioactivity about 20% than the evaporating system, and the actual radioactivity released from the evaporating and IED system were 0.473mCi and 1.098mCi, respectively. The radioactivity released from the IED was 2.32 times higher than that of the evaporating system. The dose of off-site residents was $2.97{\times}10^{-6}$mSv for the evaporating system, and $6.47{\times}10^{-6}$mSv for IED. The decontamination factor(DF) of the evaporator is, in most cases, far lower than the lower limits of detection(LLD) with the Ge-Li detector. Due to the low concentration of the liquid wastes collected from the liquid waste system, the decontamination factor of IED is very low. Since there is not enough data on the amount of solid radioactive wastes generated by the evaporation system, the comparison on these two systems has been conducted on the basis of the design, and the comparison result was that the evaporating system generated more wastes about 40% than IED.

• 자원리싸이클링
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• 제10권1호
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• pp.56-65
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• 2001

원전 안전주입계통 역지밸브의 유지보수 작업과 관련하여 작업자 방사성 피폭저감과 고가 부품의 재사용을 위해 방사능으로 오염된 이들 밸브를 화학제염법으로 제염을 수행하였다. 화학제염 후 역지밸브 내부 틈새에 잔류한 미세 고형입자를 제거하기 위해 초음파세척을 병행하였다. 역지밸브 disk arm holder를 사용한 사전 시험결과를 토대로 제염공정과 제염시약량을 결정하였으며 제염에 의한 부식산화물 용해거동, 방사능 제거거동과 재료부식거동을 조사하였다. 화학제염에 이은 초음파 적용결과, 초기 방사능의 93-95%가 제거되었으며 역지밸브 구성재질인 Type 304 stainless steel, Inconel-600 및 Stellite-6 에 대한 일반부식량은 각각 $ 2.1$\times10^{-2}$ , $6.0\times10^{-2}$ 및 1.7 mil 로써 일반부식 허용한계치의 3.3%, 24.0 % 및 2.7% 수준을 나타내어 제염효과와 재질건전성 면에서 효과적이었다.

• Journal of Periodontal and Implant Science
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• 제49권3호
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• pp.193-204
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• 2019

Purpose: The reaction of cells to a titanium implant depends on the surface characteristics of the implant which are affected by decontamination. The aim of this study was to evaluate the cytocompatibility of titanium disks treated with various decontamination methods, using salivary bacterial contamination with dental pellicle formation as an in vitro model. Methods: Sand-blasted and acid-etched (SA) titanium disks were used. Three control groups (pristine SA disks [SA group]; salivary pellicle-coated SA disks [pellicle group]; and biofilm-coated, untreated SA disks [NT group]) were not subjected to any decontamination treatments. Decontamination of the biofilm-coated disks was performed by 14 methods, including ultrasonic instruments, rotating instruments, an air-powder abrasive system, a laser, and chemical agents. MG63 cells were cultured in the presence of the treated disks. Cell proliferation assays were performed on days 2 and 5 of cell culture, and cell morphology was analyzed by immunofluorescence and scanning electron microscopy (SEM). A vascular endothelial growth factor (VEGF) assay was performed on day 5 of culture. Results: The cell proliferation assay revealed that all decontaminated disks, except for the 2 groups treated using a plastic tip, showed significantly less cell proliferation than the SA group. The immunofluorescence and SEM analyses revealed that most groups showed comparable cell density, with the exception of the NT group, in which the cell density was lower and bacterial residue was observed. Furthermore, the cells grown with tetracycline-treated titanium disks showed significantly lower VEGF production than those in the SA group. Conclusions: None of the decontamination methods resulted in cytocompatibility similar to that of pristine SA titanium. However, many methods caused improvement in the biocompatibility of the titanium disks in comparison with the biofilm-coated, untreated titanium disks. This suggests that decontamination is indispensable for the treatment of peri-implantitis, even if the original biocompatibility cannot be restored.